In cases where precise alignment is performed while receiving an external force in the case of an NC mechanism or the like, a large drive force and high rigidity are required. In order to obtain this large drive force, a method for reducing the output of the motor by means of gears and a direct drive system utilizing a large magnetic field are known.
In cases where a large drive force is obtained by reducing the output of the motor by means of gears, there is a problem that a coulomb frictional force as a result of the gears has a great effect on the alignment accuracy and, in cases where a large drive force is obtained by means of the direct drive system, there is the problem that the device then becomes large.
In the case of a linear actuator in particular, a constitution that combines a rotational motor and ball screw as a system that uses gears is known. However, in addition to the problem of alignment accuracy, a constitution that combines a rotational motor and ball screw is confronted by the problem that the device then becomes complex. Further, a constitution that utilizes a linear motor as a linear actuator of the direct drive system is known.
Furthermore, as a motor that produces a rectilinear drive force, a spiral motor, in which N poles and S poles are alternately magnetized at equal intervals in a spiral shape on a cylindrical surface to produce a rotator and a magnetic coil is disposed around the circumference on a plane that lies perpendicular to the axial direction to produce a stator, has been proposed. For example, a spiral motor of this kind is proposed in Japanese Patent Application Laid Open No. H9-56143.
A conventional motor constitution is confronted by the problem that the device becomes complex in order to obtain a large drive force. Further, in the case of the spiral motor proposed in Japanese Patent Application Laid Open No. H9-56143, the drive force is dependent on the area that lies opposite of the magnetic coil and outer circumferential face of the rotator. There is therefore the problem that it is difficult to obtain a large drive force.
Therefore, conventionally, in the case of a constitution that is known as a motor that produces a rectilinear drive force, there is the problem that it is not possible to simultaneously provide the motor with a small size and light weight, high accuracy and a large drive force.
Therefore, the present invention solves the conventional problems mentioned above and it is an object thereof to be able to simultaneously provide a motor that produces a rectilinear drive force with a small and light weight, high accuracy and a large drive force.